net.sf.saxon.lib

## Interface EnvironmentVariableResolver

- All Known Implementing Classes:
    StandardEnvironmentVariableResolver

      public interface EnvironmentVariableResolver

  This interface defines a Saxon plug-in used to resolve calls on the XPath 3.0 functions available-environment-variables() and environment-variable(). The standard implementation reads environment variables using the Java method `System.getenv()`; this can be overridden by a user-provided implementation that resolves environment variables any way it likes.

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `Set<String>` | `getAvailableEnvironmentVariables()` Get the list of available environment variables.
    `String` | `getEnvironmentVariable(String name)` Get the value of a specific environment variable

- - ### Method Detail

    - #### getAvailableEnvironmentVariables

          Set<String> getAvailableEnvironmentVariables()

      Get the list of available environment variables.
      Returns:
        a set of strings; each such string should be an acceptable argument to the method `getEnvironmentVariable(String)`

    - #### getEnvironmentVariable

          String getEnvironmentVariable(String name)

      Get the value of a specific environment variable
      Parameters:
        `name` - the name of the required environment variable
      Returns:
        the value of the named environment variable, or null if the variable is not defined. The method must not return null if the name is in the list of variables returned by the method `getAvailableEnvironmentVariables()`

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